La sclérose en plaques (SEP) est une maladie neuro-inflammatoire du système nerveux central. Les causes sont multifactorielles impliquant à la fois une prédisposition génétique et l'influence de facteurs environnementaux. Dans environ 85% des cas, les patients sont atteints de poussées correspondants à la survenue de signes neurologiques, suivis d'une phase de rémission partielle ou totale. De nombreux travaux avancent l'hypothèse selon laquelle le taux de poussées varie au gré des saisons, survenant plus fréquemment au printemps et en été. Cette fluctuation temporelle a soulevé la question de l'influence de paramètres dépendants de la saison tels que l'ensoleillement et le statut en vitamine D, le niveau de mélatonine ou encore la pollution atmosphérique. Etant donné cette variation de la pollution de l'air, nous avons cherché à explorer l'impact à court terme des particules fines (PM10), benzène (C6H6), dioxyde d'azote (NO2), monoxyde de carbone (CO) et de l'ozone troposphérique (O3), sur le risque de déclenchement de poussée, indépendamment des saisons "chaude" (1er avril au 30 septembre) et "froide" (1er octobre au 31 mars). Ce travail s'est appuyé sur les données de patients issus du réseau ville-hôpital alSacEP. Nous avons sélectionné 424 patients atteints de SEP à début rémittent et ayant connu un total de 1 783 poussées (2000-2009). Les niveaux journaliers de pollution, produits grâce au modèle physique déterministe ADMS-Urban, ont été modélisés sur une base horaire pour chaque IRIS de la communauté urbaine de Strasbourg par l'actuelle AASQUA ATMO Grand Est. De plus, une enquête individuelle menée dans le cadre de cette étude auprès de l'ensemble des patients (PT) a permis de collecter (par questionnaire téléphonique ou auto-questionnaire sur internet) des informations personnelles socio-économiques (SES) et du mode de vie pour 188 d'entre eux (PS). Enfin, le niveau SES des IRIS a été estimé à l’aide d’un indice de défaveur social - construit à partir des données du recensement de l’INSEE. Nous avons observé une influence saisonnière délétère à court terme de la pollution (3 jours précédant la poussée) sur le risque de poussée en PT, notamment de l'O3 en saison "chaude" et des PM10 et NO2 en saison "froide". Nos résultats suggèrent également que le contexte SES puisse exacerber ces associations, notamment chez les patients résidant dans les quartiers défavorisés lors d'exposition aux PM10, NO2, C6H6 et CO ("froide") et ceux résidant dans les quartiers favorisés et défavorisés lors de l'exposition à l'O3 ("chaude"). Enfin, nous avons observé chez la PS que le niveau d'éducation faible, le revenu familial moyen, la consommation de cigarette et le manque d'activité physique régulière sont les catégories SES et du mode de vie les plus associées avec le risque de poussée lors de l'exposition à la pollution de l'air. Ce travail montre la nécessité d'étudier les expositions environnementales au cours de la SEP selon une approche holistique intégrant des facteurs individuels et contextuels. / Multiple sclerosis (MS) is a neuro-inflammatory disease of the central nervous system (CNS). Causes are multifactorial enrolling both genetic predisposition and influence of environmental factors. In 85% of cases, patients experience relapse corresponding to the occurrence of neurologic signs, followed by a phase of partial or total remission. Several studies put forth the hypothesis that relapses rate varies across season, mainly occurring during spring and summer. This temporal fluctuation raised the question of season-dependent parameters influence such as sunlight exposure and vitamin D, melatonin level or ambient air pollution. Considering this variation of air pollution, we explored the short-term impact of fine particles (PM10), benzene (C6H6), nitrogen dioxide (NO2), carbon monoxide (CO) and ground-level ozone (O3), on the risk of relapse triggering, separately for "cold" (i.e., October-March) and "hot" (April-September) season. This work has drawn from data of patients provided by the alSacEP network. We included 424 patients affected with remitting MS onset who experienced 1,783 relapses over the 2000-2009 period. Daily level of air pollution was modeled through ADMS-Urban software at the census block scale of the Strasbourg metropolitan area (AASQA ATMO Grand Est). Furthermore, an individual survey was conducted among all the patients (PT) in order to collect individual socioeconomic (SES) and lifestyle features. Finally, the census block SES position was estimated using a composite deprivation index - created from the INSEE census data. A short-term (3 days preceding the relapse) seasonal adverse effect was observed in PT, in particular during exposure to O3 in "hot" season and PM10 and NO2 in "cold" season. Results also suggest that the SES context might exacerbate these associations, in particular among patients who were living in deprived neighborhood with exposure to PM10, NO2, C6H6 and CO ("cold) and those who were living in most well-of and deprived places with exposure to O3 ("hot"). Finally, we observed among Ps that low education level, average family income, smoking and lack of physical activity are more associated with the risk of relapse triggering when patients were exposed to air pollution. This work shows the need to investigate environmental exposure such as air pollution along the SEP course using a holistic approach integrating individual and contextual factors.

L'adsorption de l'ozone et du cyanoacétylène sur une surface de glace amorphe d'eau a été caractérisée par spectrométrie IRTF entre 10 et 180K. L'ozone s'adsorbe sur les OH libres de surface de la glace et une énergie d'activation de désorption de 20 kJ/mol a été mesurée par Désorption Programmée en Température (DPT) couplée à l'IRTF. Cette valeur a été confirmée par des calculs quantiques ab initio de type périodique et l'interaction a été caractérisée comme étant de type liaison hydrogène. En préliminaire au calcul périodique, les complexes O3•••H2O ont également été modélisés. Le cyanoacétylène montre deux états d'adsorption sur la surface de glace amorphe, le premier, entre 15 et 45 K, se caractérise par l'existence d'une liaison hydrogène entre les OH libres de surface de la glace et l'atome d'azote du cyanoacétylène, le second entre 45 et 110 K, met aussi en jeu une liaison hydrogène entre un doublet libre d'un atome d'oxygène de surface de la glace et l'atome d'hydrogène du cyanoacétylène. L'énergie d'activation de désorption pour le deuxième état, déterminée par DPT, est égale à 39 kJ/mol. Un caractère donneur et accepteur de proton du cyanoacétylène vis à vis de la glace est observé. Ces effets apparaîssent aussi lors de l'étude des complexes cyanoacétylène•••eau en matrice d'argon. Les stabilités relatives ont été déterminées par calcul ab initio. La nature cinétique et thermodynamique des processus d'adsorption est discutée. Une étude préliminaire de la photochimie de l'ozone co-adsorbé sur de la glace amorphe avec du cyanoacétylène a montré la formation de H2O2, de O2 et d'un troisième produit de réaction qui pourrait être un cétène.

The scope of this dissertation was to enhance our knowledge regarding the potential effects that emissions and climate change could have on air pollutants (e.g., particulate matter, ozone, Hg), in order to design effective strategies for improving air quality. A 3-D chemical transport model, PMCAMx-2008, was applied over Europe to evaluate the response of PM2.5 to 50% reduction in emissions of precursor gases (SO2, NH3, NOx, VOCs) and anthropogenic primary OA (POA). A summer and a winter simulation period were used, to investigate also the seasonal dependence of the PM2.5 response to emissions changes. Reduction of NH3 emissions seems to be the most effective control strategy for reducing PM2.5, in both periods, resulting in a decrease of PM2.5 up to 5.1 μg m-3 and 1.8 μg m-3 during summer and winter respectively. The SO2 reduction is more effective during summer, especially over Balkans. The anthropogenic POA control strategy reduces total OA, in both periods, mainly in urban areas close to its emissions sources. The reduction of NOx emissions reduces PM2.5 during the summer period, causing although an increase of ozone (O3) concentration in major urban areas and over Western Europe. Additionally, the NOx control strategy actually increases PM2.5 levels during the winter period. PMCAMx-2008 was also applied over Europe, to quantify the individual effects of the major meteorological parameters on PM2.5 levels. Our simulations cover three periods, representative of different seasons (summer, winter, and fall). PM2.5 appears to be more sensitive to temperature changes compared to the rest meteorological parameters in all seasons. PM2.5 generally decreases as temperature increases, although the predicted response is spatially variable, ranging from -8% K-1 to 7% K-1. The predicted responses of PM2.5 to absolute humidity are also quite variable, ranging from -1.6% %-1 to 1.6% %-1. A decrease of wind speed (keeping constant the emissions), increases all PM2.5 species due to changes in dry deposition (approximately 10%) and dispersion. In addition, the wind speed effects only on sea salt emissions could be significant for PM2.5 concentrations in coastal areas. Increases in precipitation have a negative effect on PM2.5 due to increases in wet deposition. Regarding the relative importance of each of the meteorological parameters in a changed future climate, the projected precipitation changes are expected to have the largest impact on PM2.5 levels, with changes up to 2 μg m-3. PMCAMx-2008 was used as part of the GRE-CAPS modeling system, to investigate the effects of climate change on PM2.5 and O3 levels in Greece. Summertime periods are simulated both for the present (2000s) and the future (2050s). Our results suggest that climate change will generally decrease PM2.5 in Greece, by 1.1 μg m-3 (5%) on average. However the predicted changes are quite variable in space, ranging from -20% to 20%. Higher levels of O3 are predicted in the future over Greece (4.5% on average). The higher future temperatures determine to a large extent the predicted O3 response Finally, the GRE-CAPS was applied over the eastern United States to study the impact of climate change on the concentration and deposition of mercury. Summer and winter periods (300 days for each) are simulated, and the present-day model predictions (2000s) are compared to the future ones (2050s). On average, atmospheric Hg2+ levels are predicted to increase in the future by 3% in the summer and 5% in winter respectively. However, the predicted concentration changes of Hg2+ vary significantly in space, ranging from -20% to 40%. Particulate mercury, Hg(p) has a similar spatial response to climate change as Hg2+, while Hg0 levels are not predicted to change significantly. Mercury deposition is also predicted to change in the future, with variable changes, ranging from -50% to 50%. The predicted response is mainly attributed to the spatially variable changes of rainfall in the future and the accompanying changes in mercury wet deposition. / Η κατανόηση των φυσικών και χημικών διεργασιών της ατμόσφαιρας καθώς και η μελέτη των αλληλεπιδράσεων του κλίματος και των εκπομπών, με τις συγκεντρώσεις των ρύπων (π.χ. ατμοσφαιρικά σωματίδια, όζον, Hg),αποτελεί απαραίτητη προϋπόθεση για την εφαρμογή αποτελεσματικών στρατηγικών μείωσης της ατμοσφαιρικής ρύπανσης. Ένα τρισδιάστατο μοντέλο χημικής μεταφοράς, το PMCAMx-2008, χρησιμοποιήθηκε για να μελετήσουμε την επίδραση που έχει η μείωση κατά 50% των εκπομπών των κυριότερων πρόδρομων αέριων ενώσεων (SO2, NH3, NOx, ανθρωπογενών πτητικών οργανικών ενώσεων) και των πρωτογενών οργανικών σωματιδίων που προέρχονται από ανθρωπογενείς πηγές (POA), στην συγκέντρωση των ατμοσφαιρικών σωματιδίων διαμέτρου έως 2.5 μm (PM2.5) στην Ευρώπη. Προσομοιώθηκαν δύο περίοδοι (καλοκαίρι και χειμώνας), προκειμένου να ελεγχθεί και η εποχιακή εξάρτηση της απόκρισης των PM2.5. Η μείωση των εκπομπών NH3 φαίνεται να είναι η πιο αποτελεσματική στρατηγική μείωσης των PM2.5, κατά την διάρκεια και των δύο περιόδων, μειώνοντας την συγκέντρωσή τους έως 5.1 μg m-3 το καλοκαίρι και 1.8 μg m-3 τον χειμώνα. Η μείωση των εκπομπών SO2 είναι ιδιαίτερα αποτελεσματική το καλοκαίρι κυρίως στα Βαλκάνια, ενώ η μείωση των εκπομπών POA μειώνει την συγκέντρωση των οργανικών και τις 2 περιόδους, κυρίως σε αστικές περιοχές. Η στρατηγική μείωσης των NOx μειώνει τα PM2.5 το καλοκαίρι, προκαλώντας ωστόσο αύξηση του όζοντος (O3) στην Δυτική Ευρώπη και τα μεγάλα αστικά κέντρα. Επιπρόσθετα, τον χειμώνα αυξάνει και τα PM2.5 στις περισσότερες περιοχές της Ευρώπης. Το PMCAMx-2008 χρησιμοποιήθηκε επίσης για να μελετήσουμε την επίδραση που έχουν διάφορες παράμετροι της μετεωρολογίας στις συγκεντρώσεις των PM2.5 καλύπτοντας τρεις περιόδους προσομοίωσης (καλοκαίρι, χειμώνας και φθινόπωρο). Τα PM2.5 είναι περισσότερο ευαίσθητα σε αλλαγές της θερμοκρασίας σε σχέση με τις υπόλοιπες παραμέτρους. Η αύξηση της θερμοκρασίας οδηγεί σε μείωση των PM2.5 και τις τρεις περιόδους. Ωστόσο, οι προβλεπόμενες αλλαγές είναι μεταβλητές και κυμαίνονται από -8% K-1 έως 7% K-1. Μεταβλητές αλλαγές των PM2.5 προβλέπονται και με αύξηση της απόλυτης υγρασίας, που κυμαίνονται από -1.6% %-1 έως 1.6% %-1. Η μείωση της ταχύτητας του ανέμου (χωρίς αλλαγή στις εκπομπές από θαλασσινό αλάτι) αυξάνει τα PM2.5 κυρίως λόγω μείωσης της ξηρής εναπόθεσης (περίπου 10%) και των διεργασιών μεταφοράς. Αντίστοιχα οι αλλαγές στις εκπομπές από θαλασσινό αλάτι (λόγω μείωσης του ανέμου κατά 10%) επηρεάζουν σημαντικά τα PM2.5 κυρίως στις θαλάσσιες περιοχές. Η αύξηση της βροχόπτωσης αυξάνει τον ρυθμό υγρής εναπόθεσης, οδηγώντας σε μείωση της συγκέντρωσης των PM2.5. Με βάση τις εκτιμώμενες αλλαγές της κάθε μετεωρολογικής παραμέτρου για το μέλλον, οι αλλαγές στην βροχόπτωση αναμένεται να έχουν την σημαντικότερη επίδραση στα PM2.5, οδηγώντας σε αλλαγές των συγκεντρώσεων τους έως 2 μg m-3. Για να μελετήσουμε την επίδραση που έχει η κλιματική αλλαγή στις συγκεντρώσεις των PM2.5 και του Ο3, το PMCAMx-2008 χρησιμοποιήθηκε σαν μέρος ενός συστήματος μοντέλων, του GRE-CAPS, το οποίο εφαρμόστηκε πάνω από την Ευρώπη, εστιάζοντας στην Ελλάδα. Η προσομοίωση του κλίματος στο παρόν και το μέλλον έγινε για την εποχή του καλοκαιριού. Τα αποτελέσματα δείχνουν πως οι συγκεντρώσεις των PM2.5 στην Ελλάδα προβλέπεται να μειωθούν στο μέλλον, 1.1 μg m-3 (5%) κατά μέσο όρο σε όλο το πεδίο εφαρμογής, ωστόσο οι προβλεπόμενες αλλαγές είναι αρκετά μεταβλητές και κυμαίνονται από -20% έως 20%. Η συγκέντρωση του O3 αυξάνει στην Ελλάδα 4.5% κατά μέσο όρο, με την αύξηση της θερμοκρασίας να καθορίζει σε μεγάλο βαθμό την απόκριση του στην αλλαγή του κλίματος. Τέλος, το σύστημα μοντέλων GRE-CAPS εφαρμόσθηκε στις ανατολικές ΗΠΑ για την μελέτη της επίδρασης της αλλαγής του κλίματος στην συγκέντρωση και εναπόθεση του υδραργύρου. Η προσομοίωση του κλίματος στο παρόν και το μέλλον έγινε για δύο περιόδους, καλοκαίρι και χειμώνας. Κατά μέσο όρο σε όλο το πεδίο εφαρμογής, η συγκέντρωση του Hg2+ στο μέλλον αυξάνεται κατά 3% το καλοκαίρι και 5% τον χειμώνα. Ωστόσο οι προβλεπόμενες αλλαγές είναι αρκετά μεταβλητές, και κυμαίνονται από -20% έως 40%. Η επίδραση της αλλαγής του κλίματος στην συγκέντρωση των πρωτογενών σωματιδίων υδραργύρου, Hg(p) είναι παρόμοια με εκείνη του Hg2+, ενώ αντίθετα δεν προβλέπονται σημαντικές αλλαγές στην συγκέντρωση του Hg0. Η αλλαγή του κλίματος επηρεάζει σημαντικά και την εναπόθεση του υδραργύρου. Ωστόσο, οι αλλαγές δεν είναι ομοιόμορφες και κυμαίνονται από -50% έως 50%. Η αλλαγή της υγρής εναπόθεσης του Hg, λόγω αλλαγής της βροχόπτωσης, φαίνεται να εξηγεί την απόκριση της εναπόθεσης του Hg, στις περισσότερες περιοχές.

The demands on health and social care organisations require professions to work more collaboratively. During pre-registration training, health care and social work students learn within practice settings, supported by practice mentors. These settings are rich learning environments to experience interprofessional working (IPW) and for students to learn together through interprofessional practice learning (IPPL). There is, however, evidence that students' experiences of both are varied or limited. The value placed on IPW, and IPPL, is therefore of interest. This thesis will investigate practice mentors' attitudes to IPW and IPPL, and explore their perspectives of the enablers and barriers to these occurring in practice settings. A mixed-methods case study approach was used to measure the attitudes of practice mentors from health and social work, and to identify enablers and barriers to IPW, and IPPL for students. Online surveys and semi-structured face to face interviews were carried out with a range of professions within one Scottish health board and associated local authority. Results showed that attitudes to IPW, and IPPL for students were generally positive. Attitudes were not significantly affected by governing body, gender, area of work, years of experience, or prior experience of IPE. IPW was perceived to be enabled by shared processes and policies, IPPL for staff, effective communication, established teams, and shared processes and policies. Proximity to other professions and shared spaces encouraged informal communication and positive interprofessional relationships. Regular structured IPPL opportunities for students were limited. However, where opportunities did occur, this was linked to areas where practice mentors perceived that there was a strong interprofessional team identity. Although attitudes to IPW, and IPPL for students are positive, further work is needed to identify systems for improving IPW, to strengthen professions' identity as interprofessional teams, and to increase IPPL opportunities for students.

In this thesis the oxidation of monoterpenes by O3 and NO2 and factors that influenced the oxidation were studied. In the environment both ozone (O3) and nitrogen dioxide (NO2) are present as oxidising gases, which causes sampling artefacts when using Tenax TA as an adsorbent to sample organic compounds in the air. A scrubber was developed to remove O3 and NO2 prior to the sampling tube, and artefacts during sampling were minimised when using the scrubber. The main organic compounds sampled in this thesis were two monoterpenes, alfa-pinene and delta-3-carene, due to their presence in both indoor and outdoor air. The recovery of the monoterpenes through the scrubber varied between 75-97% at relative humidities of 15-75%. The reactions of alfa-pinene and delta-3-carene with O 3, NO2 and nitric oxide (NO) at different relative humidities (RHs) and reaction times were studied in a dark reaction chamber. The experiments were planned and performed according to an experimental design were the factors influencing the reaction (O3, NO2, NO, RH and reaction times) were varied between high and low levels. In the experiments up to 13% of the monoterpenes reacted when O3, NO2, and reaction time were at high levels, and NO, and RH were at low levels. In the evaluation eight and seven factors (including both single and interaction factors) were found to influence the amount of alfa-pinene and delta-3-carene reacted, respectively. The three most influencing factors for both of the monoterpenes were the O 3 level, the reaction time, and the RH. Increased O3 level and reaction time increased the amount of monoterpene reacted, and increased RH decreased the amount reacted. A theoretical model of the reactions occurring in the reaction chamber was created. The amount of monoterpene reacted at different initial settings of O3, NO2, and NO were calculated, as well as the influence of different reaction pathways, and the concentrations of O3 and NO2, and NO at specific reaction times. The results of the theoretical model were that the reactivity of the gas mixture towards alfa-pinene and delta-3-carene was underestimated. But, the calculated concentrations of O3, NO2, and NO in the theoretical model were found to correspond to a high degree with experimental results performed under similar conditions. The possible associations between organic compounds in indoor air, building variables and the presence of sick building syndrome were studied using principal component analysis. The most complex model was able to separate 71% of the “sick” buildings from the “healthy” buildings. The most important variables that separated the “sick” buildings from the “healthy” buildings were a more frequent occurrence or a higher concentration of compounds with shorter retention times in the “sick” buildings. The outcome of this thesis could be summarised as follows; - - - -

<p>In this thesis the oxidation of monoterpenes by O3 and NO2 and factors that influenced the oxidation were studied. In the environment both ozone (O3) and nitrogen dioxide (NO2) are present as oxidising gases, which causes sampling artefacts when using Tenax TA as an adsorbent to sample organic compounds in the air. A scrubber was developed to remove O3 and NO2 prior to the sampling tube, and artefacts during sampling were minimised when using the scrubber. The main organic compounds sampled in this thesis were two monoterpenes, alfa-pinene and delta-3-carene, due to their presence in both indoor and outdoor air. The recovery of the monoterpenes through the scrubber varied between 75-97% at relative humidities of 15-75%.</p><p>The reactions of alfa-pinene and delta-3-carene with O 3, NO2 and nitric oxide (NO) at different relative humidities (RHs) and reaction times were studied in a dark reaction chamber. The experiments were planned and performed according to an experimental design were the factors influencing the reaction (O3, NO2, NO, RH and reaction times) were varied between high and low levels. In the experiments up to 13% of the monoterpenes reacted when O3, NO2, and reaction time were at high levels, and NO, and RH were at low levels. In the evaluation eight and seven factors (including both single and interaction factors) were found to influence the amount of alfa-pinene and delta-3-carene reacted, respectively. The three most influencing factors for both of the monoterpenes were the O 3 level, the reaction time, and the RH. Increased O3 level and reaction time increased the amount of monoterpene reacted, and increased RH decreased the amount reacted.</p><p>A theoretical model of the reactions occurring in the reaction chamber was created. The amount of monoterpene reacted at different initial settings of O3, NO2, and NO were calculated, as well as the influence of different reaction pathways, and the concentrations of O3 and NO2, and NO at specific reaction times. The results of the theoretical model were that the reactivity of the gas mixture towards alfa-pinene and delta-3-carene was underestimated. But, the calculated concentrations of O3, NO2, and NO in the theoretical model were found to correspond to a high degree with experimental results performed under similar conditions. The possible associations between organic compounds in indoor air, building variables and the presence of sick building syndrome were studied using principal component analysis. The most complex model was able to separate 71% of the “sick” buildings from the “healthy” buildings. The most important variables that separated the “sick” buildings from the “healthy” buildings were a more frequent occurrence or a higher concentration of compounds with shorter retention times in the “sick” buildings.</p><p>The outcome of this thesis could be summarised as follows;</p><p>-</p><p>-</p><p>-</p><p>-</p>

Le stannate (SrSnO3) et le titanate de strontium (SrTiO3) sont des oxydes de type pérovskite, de structures orthorhombique (Pbnm) et cubique (Pm3m), respectivement. Ces matériaux ont reçu beaucoup d'attention ces dernières années en raison de leurs propriétés physiques et chimiques intéressantes conduisant à différents types d'applications technologiques. Pour ces raisons, ces deux matériaux ont été combinés pour obtenir la solution solide de SrSn1-xTixO3, sous forme de poudres et couches minces. Au niveau des poudres, la solution solide a présenté des transitions de phases successives allant d'une structure orthorhombique à tétragonale puis cubique avec l’augmentation de la quantité de Ti4+ dans le système. Ces transitions ont été observées par affinement Rietveld des spectres de diffraction des rayons X et confirmées par spectroscopie Raman. Ces différentes structures cristallines ont conduit à des propriétés différentes de photoluminescence dans le spectre visible, l’émission variant d’une région de basse énergie vers les régions de plus haute énergie avec l’augmentation de Ti4+ dans la structure (structure orthorhombique (SrSnO3), tétragonale (SrSn0,75Ti0,25O3) à cubique (SrSn0,50Ti0,50O3, SrSn0,25Ti0,75O3 et SrTiO3). Ces émissions sont probablement favorisées par différents types de défauts formés dans le gap d’énergie de ces matériaux. Par ailleurs, les couches minces ont montré différents types de croissance qui ont été fortement influencés par la nature cristalline du substrat, la composition des films ainsi que par la méthode de dépôt utilisée (dépôt par voie chimique en solution – CSD – et dépôt par ablation laser pulsé – PLD). Les films minces déposés sur silice sont polycristallins (croissance aléatoire des cristallites), les couches sur saphir-R (Al2O3-012) sont également polycristallines mais avec une orientation préférentielle (h00) quand préparées par PLD (croissance texturée), excepté SrTiO3 qui est épitaxié avec une rotation de 45º par rapport au plan du substrat de saphir-R. Tous les films déposés sur LAO (LaAlO3-100) sont épitaxiés (h00) quelque soit la méthode de dépôt. De plus, les caractéristiques morphologiques et les propriétés photocatalytiques des films ont également été fortement influencées par ces mêmes paramètres cités précédemment. Concernant les propriétés photocatalytiques, les films préparés par la méthode CSD ont été plus efficaces que ceux obtenus par PLD et les couches de compositions plus riches en Sn4+ ont été plus actives face à la photodégradation du colorant Remazol jaune or, l’efficacité maximale étant observée pour la couche polycristalline de SrSnO3 obtenue par CSD avec un pourcentage de dégradation et de décoloration d’environ 55 et 90 %, respectivement. Le type de croissance des films de SrSnO3 préparés par les deux méthodes de dépôt a aussi montré une forte influence sur la photodégradation du colorant, les couches polycristallines d’orientation aléatoire obtenues sur silice étant plus efficaces que les texturées, elles-mêmes plus efficaces que les couches épitaxiales. / Strontium stannate (SrSnO3) and titanate (SrTiO3) are perovskite type oxides that have orthorhombic (Pbnm) and cubic (Pm3m) structures, respectively. These materials have received much attention due to their interesting physical and chemical characteristics, leading to a variety of technological applications. In this sense, these two materials were combined to each other in order to obtain powders and thin films of a solid solution, SrSn1-xTixO3. In relation to the powders, this solid solution presented successive phase transitions ranging from orthorhombic and tetragonal structures to a cubic one with increasing of Ti4+ amount in the composition. These transitions were observed by XRD Rietveld refinement of the samples and confirmed by Raman spectroscopy. The different crystalline structures of the compositions within the solid solution led to different photoluminescent properties in the visible spectrum varying the range of emission, moving from a lower energy region to a higher one with increasing of Ti4+ in the structure (from orthorhombic (SrSnO3), tetragonal (SrSn0.75Ti0.25O3) to cubic (SrSn0.50Ti0.50O3 ; SrSn0.25Ti0.75O3 and SrTiO3). These emissions were probably favored by specific defects created inside the band gap of these materials. On the other hand, the thin films of this system showed different growth orientations that are associated to the crystalline nature of the substrates, the composition of the thin films and the deposition method (Chemical Solution Deposition - CSD - and Pulsed Laser Deposition - PLD). The films deposited on silica substrate were polycrystalline (random growth of the crystallites), whereas the films deposited on sapphire-R (Al2O3-012) were also polycrystalline, with a preferred orientation (h00) for the films deposited by PLD (textured growth), except SrTiO3 which was rotated 45° epitaxially in the sapphire plane. On the contrary, all of the films deposited on LAO (LaAlO3-100) had an (h00) epitaxial growth. In addition to that, the morphological characteristics and photocatalytic properties were strongly influenced also by the same parameters described above. Regarding the photocatalytic efficiency of the films, those obtained by CSD were more efficient than the ones obtained by PLD. Moreover, the films with Sn4+ richer compositions were the most active in the photodegradation of the azo dye Remazol yellow gold, reaching a maximum efficiency with the polycrystalline SrSnO3 thin film obtained by CSD whose degradation and decolorization percentage were 55 and 90 %, respectively. The type of orientation of the SrSnO3 films showed also a strong influence on the photodegradation of the dye. The polycrystalline films with a random orientation obtained on silica were more efficient than the textured films and these ones were more than the epitaxial films. / O estanato (SrSnO3) e o titanato de estrôncio (SrTiO3) são óxidos do tipo perovskita que apresentam estrutura ortorrômbica (Pbnm) e cúbica (Pm3m), respectivamente. Estes materiais têm recebido bastante atenção nos últimos anos devido às suas características físicas e químicas interessantes, levando à diferentes tipos de aplicações tecnológicas. Portanto, estes dois materiais foram combinados com intuito de obter uma solução sólida, SrSn1-xTixO3, na forma de pós e filmes finos. Em relação aos pós, esta solução sólida apresentou transições de fase sucessivas com o aumento da quantidade de Ti4+ no sistema, passando de uma estrutura ortorrômbica à tetragonal levando à cúbica. Estas transições foram observadas através de difração de raios-X e refinamento Rietveld, e confirmadas por espectroscopia vibracional Raman. Os diferentes tipos de estrutura cristalina das composições da solução sólida levaram a diferentes propriedades fotoluminescentes no espectro visível, variando a região de emissão de mais baixa à mais alta energia com o aumento de Ti4+ na estrutura, ou seja, passando da estrutura ortorrômbica (SrSnO3), tetragonal (SrSn0,75Ti0,25O3) até à cúbica (SrSn0,50Ti0,50O3, SrSn0,25Ti0,75O3 e SrTiO3). Estas emissões foram provavelmente favorecidas pelos tipos de defeitos específicos criados dentro do band gap destes materiais. Por outro lado, os filmes finos deste sistema apresentaram diferentes tipos de crescimento os quais são associados à natureza cristalina dos substratos, composição dos filmes e com o método de deposição utilizado (método de deposição química em solução - CSD - e método de deposição por laser pulsado – PLD). Os filmes depositados sobre sílica e safira-R (Al2O3-012) apresentaram como policristalinos (crescimento aleatorio dos cristalitos), enquanto os filmes depositados por PLD apresentaram orientação preferencial (h00) (crescimento texturizado), com exceção do filme de SrTiO3 que é epitaxial rotacionado em 45º no plano da safira-R. Todos os filmes depositados através dos dois métodos de deposição sobre LAO (LaAlO3-100) apresentaram um crescimento epitaxial (h00). Além disso, as características morfológicas e as propriedades fotocatalíticas também apresentaram forte influencia dos mesmos parâmetros acima citados. Em relação às propriedades fotocatalíticas, os filmes obtidos pelo método CSD apresentaram maior eficiência que os obtidos por PLD e os filmes com composições mais ricas em Sn4+ foram os mais ativos na fotodegradação do corante azo Remazol amarelo ouro, chegando a uma eficiência fotocatalítica máxima com o filme policristalino de SrSnO3 obtido por CSD com percentagem de degradação e de descoloração de 55 e 90 %, respectivamente. A orientação dos filmes de SrSnO3 também mostrou uma forte influencia na fotodegradação do corante, sendo os filmes policristalinos com orientação aleatória mais eficiente que o texturizado e estes por sua vez mais eficientes que os epitaxiais.

Les matériaux ferroélectriques sont des matériaux qui possèdent une polarisation spontanée en l'absence de champ électrique, leur conférant plusieurs propriétés intéressantes du point de vue des applications possibles. La réduction de l'épaisseur des couches ferroélectriques vers des films minces et ultra-minces s'est avérée nécessaire notamment en vue de leur intégration dans les dispositifs de la micro et nano-électronique. Cependant, cette diminution a fait apparaître certains phénomènes indésirables au sein des couches minces tels que les courants de fuite. La caractérisation électrique de ces matériaux reste donc un défi afin de comprendre les mécanismes physiques en jeu dans ces films, d'autant qu'une information à l'échelle très locale est maintenant requise. Il est donc nécessaire de faire progresser les techniques de mesure électrique pour atteindre ces objectifs. Durant cette thèse, nous mesurons la polarisation diélectrique de l'échelle mésoscopique jusqu'à l'échelle nanométrique en utilisant des caractérisations purement électriques constituées de mesures Polarisation-Tension, Capacité-Tension et Courant-Tension mais aussi des mesures électromécaniques assurées par une technique dérivée de la microscopie à force atomique et nommée Piezoresponse Force Microscopy. Au cours de nos travaux, nous montrons la limite de certaines techniques de caractérisation classiques ainsi que les artéfacts affectant la mesure électrique ou électromécanique et pouvant mener à une mauvaise interprétation des résultats de mesure. Afin de pousser nos investigations plus loin, nous avons développé de nouvelles techniques de mesure pour s'affranchir de certains signaux parasites dont nous exposerons le principe de fonctionnement. Nous présentons les premières mesures directes de polarisation rémanente à l'échelle du nanomètre grâce à une technique que nous nommons nano-PUND. Ces techniques et méthodes sont appliquées à une variété importante de matériaux tels que Pb(Zr,Ti)O3, GaFeO3 ou BaTiO3 dont, pour certains, la ferroélectricité n'a jamais été démontrée expérimentalement sans ambiguïté. / Ferroelectric materials show a spontaneous dielectric polarisation even in the absence of applied electric field, which confers them interesting possibilities of applications. The reduction of the thickness of ferroelectric layers towards ultra-thin values has been necessary in view of their integration in micro and nano-electronic devices. However, the reduction of thickness has been accompanied by unwanted phenomena in thin layers such as tunneling currents and more generally leakage currents. The electrical characterization of these materials remains a challenge which aims at better understanding the physical mechanisms at play, and requires now a nanometric spatial resolution. To do so, it is thus mandatory to enhance the techniques of electrical measurement. In this work, we measure the dielectric polarisation of ferroelectric films from mesoscopic scale down to the nanometric scale using purely electric characterisation techniques (Polarisation vs Voltage, Capacitance vs Voltage, Current vs Voltage), but also electro-mechanical techniques like Piezoresponse Force Microscopy which derives from Atomic Force Microscopy. We show the limits of several classical techniques as well as the artefacts which affect electrical or electro-mechanical measurement and may lead to an incorrect interpretation of the data. In order to push the investigation further, we have developed and we describe new measurement techniques which aim at avoiding some parasitic signals. We present the first direct measurement of the remnent polarisation at the nanoscale thanks to a technique which we call « nano-PUND ». These techniques and methods are applied to a large variety of materials like Pb(Zr,Ti)O3, GaFeO3 or BaTiO3 which (for some of them), ferroelectricity has not been measured experimentally.